lumens of fluorescent tubes

This is a discussion on lumens of fluorescent tubes within the Beginner Planted Aquarium forums, part of the Beginner Freshwater Aquarium category; -->
I while back I posted this lumens ratings chart for the most popular flourescant bulbs. These are just estimates. Actual values vary by Kelvin ...

Lumens is the amount of light seen by the human eye. It has absolutely nothing to do with plants. Our eyes peak in the green spectrum of light. Some have probably noticed at one point, 2 lightbulbs of the same wattage may have different brightness. It would seem obvious that the brighter one would be better, however that is not always the case. This is the spectrum we are able to see. Lumens again is a measure of the light visible to the human eye. Plants on the other hand reflect green light(they cannot use green light). Plants need light with peaks in the red, blue, and yellow spectrum. This is the spectrum plants can use.

In general the spectrum we see and the spectrum plants depend on is almost opposite. So, picking bulbs based on lumen value is a very poor way to choose a bulb for plant growth. It is easy to determine, a green bulb is going to have a very high lumen rating, plants however will die under green light. So if you are lighting your house it would make sense to go for a bulb with a higher lumen rating. Plants on the otherhand may perfer bulbs with lower lumen rating. This bulb may look dimmer to us, but may indeed be more efficient for the plant.

So how to choose a bulb? There are many sites that list the reported PAR efficiency of specific brands of bulbs.(here and here) PAR is a measure of the light that is usable in photosynthesis. If or when you are looking for new bulbs it is helpful to pick a bulb with a known high PAR rating. Since this is not know on most bulbs and is not list on the package of any, another way is to look a the bulbs color spectrum. Generally, the more closely to resembles the spectrum a plant uses the more efficient the bulb should be. Though this does not take in account the Kelvin rating or visual appearance. Its best to pick a bulb with a good spectrum and a ideal kelvin rating. Kelvin rating is dependent on the user though, it is whatever looks best to you.

So this is the spectrum a plant uses in general.

This is the spectrum PAR measures.
Here is the reported spectrum of your original Colormax lights, sometimes these are on the package, sometimes the internet, sometimes they don't exist (if you buy a cheap bulb).

This is my perfered bulb GE 9325K, it doesn't have a T5 version though, just PC and T8s.

This is the spectrum measured by lumen

Woot! Now I'm done, since I've probably bored you all. In the end light is very complex. If you ever bother to really go indepth with it, you will eventually figure that despite all the fancy fixtures we buy and specilized bulbs we use. Cheap spiral compacts will generally do the job just fine. They may not be as efficient, as t8's, t5, pc, ect.(depending on the bulb). Usually no spectrum, just a kelvin rating to go off of.

That's for the colormax. Here's the only one I could find for my 6700.

It looks closer to your bulb than the Colormax. The Colormax bulb I have is strictly for showing off the color in my fish. While the 6700 has an orange/yellow tint, the Colormax is more of a balanced white.

I don't disagree with you. But I would use Lumens over watts when determining the intensity of light. But when I use the lumen ratings, I'm using it to compare two similar Kelvin rated bulbs. For example, comparing a 40watt t-8 daylight bulb to a CFL 65watt daylight bulb. In this case the lumens should be a good mearure. I would not use the Lumen rating alone to choose a bulb.

With the variety of all bulbs you have these compared to a few yrs back when all pretty much was t5 you just HAVE to look at everything not just one factor, you wanna check wattage, kelvin and lumens and then go from there for the size tank you've got really. That's the same I did for my 55g when I lowered it to 32w only and then had a "daylight" and "sunlight" GE bulb and determined based of the lumens which one alone will go in there and the plants sure approve even the narrowleaf chain sword which we all thought wouldn't make it.

I really think thou in spoot's case here with the new light he has, some pennywort for some top cover now, he's all set with his plants now. Fine tune it with some ferts and all will go well from there.

So far something seems to going right. Getting some new growth on my java and african ferns, also getting cabomba growth also. I moved both of my anubias under the floating pennywort (with bonus duckweed) that Angel gave me. My NO bulbs will be in tomorrow.

Happened upon a 46 Gallon Bow this weekend also. Getting it set up and ready. I can't seem to find the GE Daylights in T8 36", and haven't seen any GE 9325 (Aqua-Rays?) at all. Still looking though. No luck at the Crossville Lowe's. Going to check here today.Posted via Mobile Device